This proposal describes an experimental approach to study the role of the hormone relaxin in gestation and parturition. Specific projects include: 1) electrophoretic isolation of specific molecular species of relaxin from crude relaxin preparations; 2) investigations of the biological capabilities of the isolated fractions; 3) use of radioimmunoassay to study levels of the hormone in sera and tissue extracts; 4) utilization of the fluorescein labeled antibody technique to identify cells and tissues that contain relaxin.